Desktop Pick-&-Place Machine: An EETimes Community Project

Would you be interested in having your own pick-and-place machine that can assemble your boards -- and possibly even reflow them -- while fitting in a space smaller than an 11" x 17"?

With all the excitement associated with of 3D printers, there seems to be a giant gap in the rapid prototyping tool set -- a desktop pick-and-place (P&P) machine that can be had at a reasonable price. If you were to survey the landscape, you would find that most of the smaller pick-and-place machines that are out there are either just not quite ready for primetime, or will cost more than a few thousand dollars. This is where the EETimes community has an opportunity to change the picture.

The idea started at this year's EELive! Conference and Exhibition. A few of us were standing around at one of the Gadget Smackdowns chatting about this and that. Among the various topics we discussed were the popularity of presentations on mechanical design and the need for a way to get reasonable prices on low-volume production/prototype runs. It was then that these two ideas converged and we decided that we wanted to design a very small pick-and-place machine.

The more we talked about this, the more excited we got. The thought of having a machine that can assemble your boards -- and possibly even reflow them -- while fitting in a space smaller than an 11" x 17" footprint just brought great big grins to our faces.

This idea -- with the excitement it brings -- is more than just designing a machine. There is a teaching opportunity as well. We will be using this project to teach concepts about electromechanical integration, motor usage, computer vision, PCB assembly, and a range of related topics through our blog posts and future conference presentations.

So what exactly will this machine consist of, and what tasks will it be capable of performing? Well, this is where we would appreciate your help. We do have some basic goals, but we would welcome your suggestions to fill out the details.

Let's start with out top-level design goals, which are as follows:

$400 to $600 target sales price

11" x 17" or smaller footprint

A modular system allowing for addition of features at a future date

Good mechanical design

With these as the basic design goals, here are some thoughts on other details to get your creative juices flowing. Because of the fact that we are shooting for a low price point, there will need to be some tradeoffs. For example, this is not intended to be the fastest pick-and-place machine out there, so we can look at compromising on speed.

Also, because we are not intending to use this machine to provide high throughput, we can look at eliminating the typical component feeders (though we may have a concept that could mitigate this tradeoff). Lastly, because we are looking to have a small machine, we are not intending to have an extremely large build area. Remember that this is intended to be a machine for very low volume production -- say a few hundred pieces, or prototypes.

There is an advantage to this being a small machine, which is that we can look at employing some concepts that might be too complex to implement on a production-level machine. For example, one concept we would like to consider is making this machine so that it cannot only print solder paste without stencils, but that it can then be able to reflow the entire board after the components have been placed. Another idea is to have a component tester. This concept would allow for testing of polarity of LEDs and other diodes. In turn, this would help insure less iterations of your concept due to mislabeled diodes.

So we have a basic framework and some design concepts to get the gears turning in your head. Now we need your help to gather ideas on what you would like to see in this type of a machine. We encourage you to share your comments below. After everyone has posted their ideas, we might use a poll tool to help narrow down some of these concepts. Once we have a better idea as to what the community would like to see in such a machine, there will be further chances to participate in this project. We look forward to seeing your creativity in action.

The biggest issue is that copper is very effective reflecting many frequencies of lasers, though one thing that I have seen as an effective solution a while back was where they painted the dual layer board with black spray paint. They then used a very cheap laser that was pulled from a blueray player to etch the paint. Once this was done, it was placed in a dip tank and etched.

One might be able to take this a step further and after you have etched the board, then remove the original paint mask. Then apply solder mask over the entire board, and etch the doler mask to expose the pads. This could be a rather interesting thing. I am not sure that it would work, but would be interesting to see.

The challenge that our machine would have is that we currently get to cheat in the sense that the path is not important, we just need to get from point A to point B. Doing laser etching, we would have to do a specific path. This would get trickier, but I am sure not impossible.

I have gotten to the point that for all the boards that are under a few square inches that it is just too easy to get the from OSHPark.

@adam - I wonder if you could get a light (ie not heavy) laser that would make holes in PCB? itf so it would be lighter than a motorised drill. But I don't know anything about the capabilities of laser diodes. And you might have problems from carbonising the edges of the PCB, hence making a semi-plated-thru hole.... Do you or anyone else know more about lasers? I had an idea to use an x-y plotter mechanism with a UV laser to print-expose pre-coated PCB without going to the hassle of having a positive transparency, I'm not sure if that's what the Bread-Box PCB maker guys are doing....

Though I do have to admit that it is inline with some of the goals that have been set out for this device. Having interchangable heads has always been one of the concepts. It allows for you to have a solder dispensing head and a vacuum head, and then to be able to mount a camera if needed. So adding one more head, that is not a huge deal, and because this is something that could most assuridly be done with a high speed brushless motor from the hobby side of things, then it is not all that difficult. Designing the spindle so that it is accurate will be the greatest trick.

If once everything else is done, and it works without modification, then we will go for it. That is after we have gotten all the other base model things working.

I see that you are mentioning the C5030 and C5055 but have you taken a look at the C5047 device? The only reason that I mention it is that it has not only a serial digital out, but it also has a standard quaderature interface. In other words, it acts as a drop in encoder replacement. This could simplify any roll our own efforts as we may be able to completely leaverage a dev kit from one of these motor control solutions with little modifications to their code. This could make the transition to a BLDC servo solution very palitable.

As an announcement to all those that are reading, Bob (aka salbayeng) has been invited to participate in an official capacity with this project. I think that all of us have been able to learn from his very detailed posts.

He sent me his detailed calcs in the spreadsheet that he pulled these numbers from, and it is top notch work. We should look forward to seeing more from him as he has indicated that he is willing to do some guest posts for us.

Hi Adam -- did you see this Desktop PCB Printer project? Actually, it's more of a desktop PCB etcher.

But the point is, there's a lot of talk about the problem of drillig holes in PCBs. If your pick-and-place machine were modular, would it be possible tow swap the "place" head for a "drill" head and actually drill through-hold PCBs?

Hi Adam, looked at the numbers in your last post, call this AC1, put them in a spreadsheet , errors looked good, but very high motor speed and low torque utilisation. So toned it down a bit , AC2 used a coarse leadscrew of 0.5", and only 2g accel, and trapezoidal speed profile. So now have manageable motor speeds but larger errors, would need a second 1024count encoder somewhere?. (I've randomly called the error budget 0.1mm)

Alternate case AC2:has 10x longer lead (0.5") , and trapezoidal velocity profile with 2g max.Has some error problems, e.g. 152% of budget if we want to hold using 12step mode. Magnetic encoder 49% of budget.Total travel time = 240msMax motor=7500rpm Torque=.01Nm (2% of motor spec)OK now we are doing 60MPH in 2nd gear

I guess what all this says is we need to match the motor and gearing to the payload and error requirements. Most commercial PnP machines have very coarse gearing (consider a typical 1"diameter toothed belt pulley has a 3.142" lead)

Yes, the BeagleBone black is high on the list of parts that we anticipate using. We were able to speak to Jason Kridner at EELive and he said that he would be willing to help get us pointed in the right direction.

As to the encoders, I really think that it will depend on the overall stiffness of the system. If you are mounting to the opposite end of a 3/8" leadscrew that is only 10 inches long, then at the maximum capacity of a plastic leadnut (which we would not be running at) the deflection due to torque would be .8°. This would be a 350 lb load. If we were to say that the gantry head weighed .5 lbs and we were to be running at a max accel of 10g's, then the deflection would be .01°. For an encoder to be able to register this, it would need to be over 30,000 counts per revolution.

As for going with the Geko drives, that is probably out of the range of what we are able to handle. Most likely we will have to leverage some other solutions that are already out there.

We did just get some information from Trinamic on a new dev kit that they have. This is something that we may want to look at. I know that the TI solution is a full closed loop control for BLDC motors, essentially creating a servo motor. I have a feeling that we are going to have a lot to learn in this area.